Editing Quantum tunnelling (section)

==== Kinetic isotope effect ====
{{Main|Kinetic isotope effect}}

In [[chemical kinetics]], the substitution of a light [[isotope]] of an element with a heavier one typically results in a slower reaction rate. This is generally attributed to differences in the zero-point vibrational energies for chemical bonds containing the lighter and heavier isotopes and is generally modeled using [[transition state theory]]. However, in certain cases, large isotopic effects are observed that cannot be accounted for by a semi-classical treatment, and quantum tunnelling is required. [[Ronnie Bell (chemist)|R. P. Bell]] developed a modified treatment of Arrhenius kinetics that is commonly used to model this phenomenon.<ref>{{Cite book |last=Bell |first=Ronald Percy |title=The tunnel effect in chemistry |date=1980 |publisher=Chapman and Hall |isbn=0412213400 |location=London |oclc=6854792}}</ref>